The present invention generally relates to the cooling of electronics in an electrically driven refrigeration system, in particular in a vehicle air conditioner.
It is known to cool the passenger compartment of an automotive vehicle by means of an electrically driven refrigeration system, also referred to as electric air conditioner. Such a refrigeration system typically comprises an evaporator disposed in the interior of the vehicle, a refrigerant compressor driven by an electric motor, a condenser located in the engine compartment and an expansion valve. Refrigerant is pumped by the compressor through the condenser, the expansion valve and the evaporator.
It will be noted that the electric motor of the compressor is sometimes controlled by an electronic controller, which generates some heat that needs to be dissipated.
In order to cool down the electronic controller of the electric motor, it has been proposed in WO 00/50826 to arrange the electronic controller so as to be in thermal exchange relationship with the refrigeration circuit between the exit of the expansion device and the compressor inlet, that is on the low pressure side of the system, where the refrigerant is at a temperature of a few degrees Celsius. If such an arrangement does indeed allow to cool the electronics with the refrigerant, which is at its lowest temperatures, it has the important disadvantage that the temperature of the refrigerant is increased. This results in an overall reduction of system performances, in particular having regard to efficiency and capacity.
In U.S. Pat. No. 4,720,981 it is has been proposed to arrange the electronic controller of the compressor motor in the refrigeration circuit between the condenser and the expansion valve so as to be in thermal exchange relationship with the refrigerant. This again impairs the cooling efficiency of the system since the refrigerant is heated by the electronic controller where it should normally be about ambient temperature, just before entering the low pressure side.
The object of the present invention is to provide an alternative way of cooling the electronic controller of the motor driving the compressor in such a refrigeration system. This object is achieved by a system as claimed in claim 1.
An electrically driven refrigeration system in accordance with the invention comprises a compressor, an electric motor for driving the compressor and an electronic controller for controlling the electric motor. The system further includes an expansion device, a condenser and an evaporator, which are interconnected with the compressor in such a way as to form a refrigeration circuit with a circulation of a refrigerant from the compressor through the condenser, the expansion device and the evaporator back to the compressor. According to an important aspect of the present invention, the electronic controller is arranged in such a way as to be in thermal exchange relationship with the refrigerant at a point of the refrigeration circuit situated between the compressor outlet and the condenser outlet.
Hence, in the present electrically driven refrigeration system, the electronic controller is arranged on the high pressure side of the refrigeration system, at a point of the refrigeration circuit after which the refrigerant will subsequently flow into the condenser. It follows that the extra heat absorbed by the refrigerant on contact with the electronic controller will be largely dissipated in the condenser. The refrigeration system of the present invention proves particularly advantageous over the refrigeration systems described in WO 00/50826 and U.S. Pat. No. 4,720,981, since the extra heat due to the electronic controller will not affect the temperature of the refrigerant in the low pressure side, whereby compressor efficiency in particular is barely affected. The present refrigeration system thus allows for cooling of the electronic controller and has an improved cooling efficiency.
A further advantage of the present refrigeration system is that the electronic controller is physically closer to the electric motor, which simplifies the wiring of the refrigeration system. This also means that, for compactness, the electronic controller may e.g. be integrated in a single housing comprising the compressor and its motor.
In a preferred embodiment, the refrigeration system comprises an auxiliary loop, which is associated with the condenser and connected thereto in such a way that at least part of the refrigerant flows out from the condenser into the auxiliary loop at a first point of the condenser and is reintroduced in the condenser at a second point downstream of the first point. The electronic controller is arranged so as to be in thermal exchange relationship with the refrigerant circulating in this auxiliary loop. In this embodiment, the electronic controller is cooled by the refrigerant, which has already lost part of the heat that was absorbed during the evaporation and compression processes. The remaining heat and the extra heat generated by the electronics will be rejected from the refrigerant in the second part of the condenser, i.e. upon its reintroduction at the second point. It follows that the refrigerant temperature downstream of the condenser is not at affected by the cooling of the electronic controller.
The heat exchange between the electronic controller and the refrigerant may result from direct or indirect contact. Indeed, the assembly of the controller and the refrigeration circuit may be such that the components to be cooled are directly in contact with the flow of refrigerant. This is mainly applicable in the automotive industry, which employs low voltages and particularly well insulated electronic and electric parts. Alternatively, the electronic controller casing may e.g. be mounted to be in close contact with the refrigerant piping between the compressor and the condenser, so that heat is exchanged through the walls of the casing and of the refrigerant piping. Another possibility is to mount the electronic components on a block of material comprising one or more internal channels in which the refrigerant is circulated.
In practice, it may be advantageous to take into account the extra heat to be dissipated in the condenser in the condenser specifications at the design stage of the refrigeration circuit. This means that a slightly bigger condenser than usual may be used to ensure an optimal operation of the refrigeration system.
It remains to be noted that the refrigeration system in accordance with the present invention may be used in various air conditioning applications such as e.g. in vehicle air conditioning systems (e.g. for cars, trucks and the like or agricultural and construction works vehicles) as well as in residential or commercial air conditioning systems. Moreover, a heat pump system may be adapted in such a way as to function according to the refrigeration system of the invention when operating in the cooling mode.